Sullivan Slough (Des Moines County) is a bottomland floodplain wetland (i.e., a river swamp) with two neighbors next door; both neighbors are critical to the life of this wetland. The obvious neighbor is the Mississippi River—the slough is essentially a backwater on the river, flooded when river levels are high. The other neighbor is the Burlington generating station, a coal-fired power plant whose stack is visible from the swamp.
We’ve discussed the connection between the river and adjacent floodplain wetlands, such as when we visited Mount Sterling Marsh in Van Buren County, and last week at Sny Magill in Clayton County (connecting the wetland both to the adjacent Mississippi River, and to air pollution—from nuclear weapons (!!). Here at Sullivan Slough, the river had been high enough to make access to this site impossible until just before my trip; the evidence of recent flooding was obvious.
What is less obvious is the connection between the power plant and the wetland. Flooding by the river makes it more complicated; river water can bring things in or carry things out of the swamp. High enough water will overwhelm the access road or other barriers. The wetland will be inundated (swamped) with river water.
In addition to the effects of the river flooding, the wetland will receive pollutants from the power plant next door. The smoke stack spreads air pollutants far and wide; only a small fraction will land in this slough. But, some of it will. And emissions are significant. According to EPA data for 2014 (most recent available), 3657 tons (3300 metric tons) of sulfur dioxide was released by the plant; this reacts with moisture in the air to form sulfuric acid, a component of acid precipitation (“acid rain”). Likewise, nitrogen oxides produce nitric acid; the plant emitted just over a thousand tons (900+ metric tons). In 2005, the plant released 55 pounds (25 kilos) of mercury. Compared to many tons of other pollutants, that seems negligible; yet mercury is very toxic, and it becomes concentrated as it moves up the food chain. And mercury is a liquid metal…it doesn’t biodegrade. Mercury is forever. The EPA also has information about mercury from power plants, and efforts to control this major source of pollution.
But let me end with some good news: that power plants is scheduled to become a better neighbor. According to a report from the Sierra Club, the plant “Will transition from
coal by December 31, 2021”—something to make us all breathe a little easier…especially the life at Sullivan Slough.